A U.S. judge temporarily blocked President Donald Trump’s planned ban on transgender Americans serving in the armed forces, ruling that an earlier policy of inclusion must remain in effect.

The ban, promised by Trump in a series of tweets in July and due to be implemented in March 2018, is a form is discrimination based on gender and is already causing harm to affected personnel, U.S. District Judge Colleen Kollar-Kotelly in Washington said in a ruling Monday.

“There is absolutely no support for the claim that the ongoing service of transgender people would have any negative effect on the military at all,” the judge wrote. “In fact, there is considerable evidence that it is the discharge and banning of such individuals that would have such effects.”

Citing threats to troop readiness and morale, as well as costs associated with transgender medical services, Trump said he would reverse former President Barack Obama’s policy allowing transgender soldiers to serve. The suit by the National Center for Lesbian Rights claims the plan violates the Equal Protection clause of the Constitution.

The judge said she was required to apply a greater degree of scrutiny to the government’s plan because it impacts a class of Americans that has lacked political power.

“As a class, transgender individuals have suffered, and continue to suffer, severe persecution and discrimination,” the judge wrote. “Despite this discrimination, the court is aware of no argument or evidence suggesting that being transgender in any way limits one’s ability to contribute to society.”

More than a dozen states filed a joint brief earlier this month in support of the plaintiffs, accusing the Trump administration of peddling discredited myths to justify an “irrational” return to military discrimination. More than a dozen other nations that already accept transgender troops, including Canada, Britain and Israel, report none of the problems cited by the president to justify the ban, the states said.

Three anonymous “Jane Doe” plaintiffs in the case serve in the U.S. Army, including Doe 3, who has already served in Afghanistan and “expects to be deployed to Iraq soon,” according to their complaint. Another plaintiff is a 20-year U.S. Air Force veteran, who has served two tours of duty in Iraq.

The proposal is among several moves by the administration targeting rights gained in recent years by transgender Americans, including reversing guidance by Obama directing public schools to allow students to use the bathrooms for the gender they identify with.

The case is Doe v. Trump, 17-cv-01597, U.S. District Court, District of Columbia (Washington).